1. Field of the Invention
This invention relates generally to cross drive steering transmissions and, more particularly, to a novel arrangement of modular components whereby single centerline simplicity is achieved.
2. Description of the Prior Art
Cross drive transmissions, widely used in track laying vehicles, typically include rotary power input at the longitudinal centerline of the vehicle and rotary power output shafts at opposite ends of the transmission on a common centerline of the latter extending perpendicular to the vehicle's longitudinal centerline. For steering, a pair of planetary differentials or combining gear sets are provided, each including a rotary power output member connected to the corresponding transmission output shaft, a range input member driven by range gearing in the transmission, and a reaction or steer input member driven in either of two opposite directions by an infinitely variable ratio drive such as a hydrostatic pump/motor unit. To steer the vehicle, a speed differential is created between the transmission output shaft by driving the reaction members of the two combining gear sets at identical speeds but in opposite directions. The combination of rotary power input at the center and rotary power output at opposite ends of the transmission and steering through combining gear sets presents a complex packaging problem which has, in the past, produced transmissions having multiple centerlines about which various component groups of the transmissions rotate. Such multiple centerline transmissions, while functionally adequate, require substantial space within the vehicle and virtually complete disassembly for service. A cross drive steering transmission according to this invention has range gearing, steer drive, steer transfer, and combining gearing packaged in modules on a single centerline and, therefore, represents an improvement over heretofore known cross drive steering transmissions.